Better Robotic Surgeries Possible as Scientists Develop New Physics Law on Friction

Robots have long been used in manufacturing assembly lines and medical technology. Still, scientists and engineers have encountered difficulty in having these devices do complex handwork such as holding or gripping objects, specifically in wet environments.

That became the focus of the study entitled "Elastohydrodynamic friction of robotic and human fingers on soft micropatterned substrates" published in Nature Materials. In the study, it was revealed that researchers have discovered a new law of physics that accounts for this type of friction, which would lead to more advanced robotic devices.

Dr. Lillian Hsiao, assistant professor of chemical and biomolecular engineering at North Carolina State University and corresponding author of the study, said that their research would lead to the creation of more reliable and functional haptic and robotic devices, in such applications as manufacturing and telesurgery.

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Addressing Elastohydrodynamic Lubrication Friction

Researchers are addressing the issue of elastohydrodynamic lubrication (EHL) friction, which Science Direct defines as the typical regime for friction pairs having elastic contact under very high pressure in unconformal contact.

This occurs when two solid surfaces get in contact with a thin layer of fluid between them. This occurs when we rub the tips of our fingers with the thin layer of natural oil from our skin. This could also apply to a robotic claw carrying an object coated with oil or a surgical device used inside the body.

Friction, the researchers said, is important because it assists us in grasping things efficiently without dropping them. It is extremely difficult, Hsiao said, to account for EHL in developing materials that manage grasping capabilities in robots.

Developing materials that manage EHL friction, engineers need a framework used in a wide variety of patterns, materials, and dynamic operating conditions, which is behind the principles of the new law of physics the researchers discovered.

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New Law Utilized for Better Robotic Grasps

The law can be utilized to account for FHL friction and can be used in various soft systems or objects, as long as the surfaces are patterned, Hsiao added. Such surface patterns include slightly raised surfaces on our fingertips to the robotic tool surface grooves.

The new law, developed by Hsiao and her graduate student Yunhu Peng, uses four equations to account for all physical forces at play in understanding EHL friction.

In their research, the engineers demonstrated the law in three systems: human fingers, a bio-inspired robotic fingertip, and a tool called a tribo-rheometer used to measure frictional forces.

Findings are seen as tremendously helpful in developing robotic hands that have nuanced controls for reliably handling manufacturing processes, a Forbes article said. But the most obvious application is telesurgery, wherein surgeons remotely control robotic devices for surgical procedures. Such results, researchers said, is a step forward in understanding touch and controlling touch in synthetic systems.